Electric insulator



Jan. 2, 1934. E. BURKE ELECTRIC INSULATOR Filed March 18. 1931 e ck .Y I.

l 1 E p o vw,... u l/l W h IM E Patented Jan. 2, 1934 NETE .S-"'i"ATES PATENT orifice Brown Company, Portland,

ration of Maine Maine, a corpo- Application March 18, 1931,. Serial No. 523,475

7 Claims.

This invention relates to insulators for high tension lines or like installations where great dielectric strength is required and where the insulator itself must be of such tensile strength as to withstand the stresses and strains of heavy wire suspensions.

It has been repeatedly proposed to form such insulators of fibre which as a material offers many possibilities over porcelain or like fragile material as the breakage of such insulators is a high item of expense in line building and maintenance.

The great difficulty has been to combine strength factors with those of insulating properties so as to produce a practical unit because while fibre has great advantages in connection with impregnation, it has not in itself the required tensile strength for such parts as the load carrying stems of, petticoat or hooded types of insulators.

A suggested solution of this difiiculty has been that of combinations of material which would supply the required factors but such combinations have developed leakage at joints or like areas and the efficiency of the insulator has thus been lost.

As 1 have analyzed the problem of such insulaters there is the tensile factor of suspension or support and the dielectric factor which must be so combined that the dielectric will enclose and insulate the suspension member such as a core so as to make it a part of the whole; yet so combined that the core will relieve it from undue stresses and strains between its ends.

To accomplish the desired results and attain the required characteristics, I have provided a basis of combination by which insulators including hoods or petticoats of molded fibre are given high tensile as well as high dielectric strength.

jIn such combination I preferably use an inner stem of some strong wood. Such stems have previously been suggested but such alone does not solve the problem. The insulating members must constitute what is practically a continuous and substantially homogeneous unit.

Continuity is essential as cracks or crevices allow leakage. Homogeneity is important because by substantial homogeneity such cracks or crevices may be avoided and prevented.

As illustrative of the principles involved, I have shown in the accompanying drawing as an example, a conventional type of insulator and one heretofore presenting maximum difficulties.

In the drawing:

Fig. l is a vertical section of an insulator construction in accordance with my invention.

Figs. 2, 3 and 4 show various types of wedges capable of use therein, and

Fig. 5 is an end View showing the metal cap for 6c the end of the stem showing a fragment of an insulator hood.

Such an insulator includes a core 1 of any suitable natural Wood growth such as of maple, ash or similar well grained trees. Completely covering this core 1 is a tubular nbre sleeve 2 which, as shown, consists of plural tubes of fibre stock, 2a, 2b and 2c, 2c being provided externally with continuous screw threads 3. These are close fitting and pushed on in assembly under 7u heavy pressure.

Threaded on the exterior of the tube 2 are insulating members 4. These as shown are hood or skirt members of fibre composition preferably of wood fibre pulp or stock. They are suitably spaced from each other by intervening members 5 also of the same fibre or other material as the hoods 4 and the composite tube 2. The spacers 5 are screw threaded to correspond to the screw threads of the tube 2.

These fibrous members are preferably irnpregnated prior to assembly. The assembly is also impregnated and coated by a suitable compound such as of bitumen or asphaltic nature as for example gilsonite or like material.

The core 1 and tube 2 may be produced in various lengths according to the length of the core or number of hoods 4 and spacers 5 required, and when impregnated as above form a homogeneous and continuous body.

In order to seal the ends of the unit I provide metal end members 6 which have internal screw threads adapted to engage the threads of the tube 2 above and below the outermost hoods 4 and spacers 5. The outer ends of these caps 6 each are provided with ears 7 having apertures 71 through which connecting members may be passed to fasten the insulators in position.

In order to secure the assembly cap 6 on the core 1 and tube structure 2 and maintain such 100 t even under the strains of use, I provide the ends of the core 1 with a kerf or kerfs K into which is driven a wedge which may be of any of the types shown in Figs. 2, 3 or 4. Such wedge is held in the kerf under compression by the caps 6 thus making a tight connection between the parts.

The wedge member W as shown in Fig. 2 is a simple or single wedge. That shown in Fig. 3 and indicated as W is a double or composite wedge. member.

The lower edges of the spacers 5 and end members 6 are beveled as at 5 and 6 so that in assembly under compression they are forced into the contacting surface of the hoods 4.

Such an insulator is dielectrically homogeneous and unitary in spite of the fact that within is the wooden core or stem. structurally from the viewpoint of its eiective tensile strength it is of high efciency.

Its wooden stem and the surrounding tubes forced on under pressure and capped and end wedged form together a suspension or supporting unit which can be made with wide factors of safety. No attempt has been made to indicate impregnation or coating. These may be as many and of such nature or natures as may be required.

Various modifications in the materials or impregnations used, the relation of one part to the other, and the number and size of hoods and spacers employed may all obviously be resorted to without departing from the spirit of my invention if within the limits of the appended claims.

What I therefore by Letters Patent is:

1. An insulator of the class described comprising a cylindrical dielectric stein investment of fibre, fibre hood members spaced thereon and all impregnated and sealed by a dielectric penetrant and a core of relatively high tensile strength tightly lodged within said tubular stem investment and terminal connecting members end sealing said tube and tightly embracing said tube and core ends whereby tensile strains are transmitted through the core to the relief of the surrounding brous dielectric insulation.

2. An insulator of the class described comprising a cylindrical dielectric stem investment of bre, nbre hood members spaced thereon and all impregnated and sealed by a dielectric penetrant and a core of natural woody growth and The wedge W2 of Fig. 4 is a conical claim and desire to secure of relatively high tensile strength tightly lodged within said tubular stem investment and terminal connecting members end sealing said tube and tightly embracing said tube and core ends whereby tensile strains are transmitted through the core to the relief of the surrounding ibrous dielectric insulation.

3. An insulator, comprising a stem, consisting of a wooden core, and a tubular nbre sleeve thereon, said sleeve having a threaded exterior, alternate hood members and spacers screwed on said threaded sleeve, and an end fastening having an engaging edge compressibly engaging the end of the assembly and sealing the stem.

4. An insulator, comprising a stem, consisting of a core, and a tubular fibre sleeve compressibly lodged thereon, said sleeve having a threaded exterior, spaced hood members screwed on said threaded sleeve, and end fastenings sealing the stem ends.

5. An insulator, comprising a stem, consisting of a wooden core, and a tubular ber sleeve thereon, a metal cap at each end of the stem, one of said caps being threaded to the bre sleeve end and wedged to the end of the wooden core, hood members threaded on said sleeve and internally threaded tubular spacers on said sleeve between said hood members, said assembly on the stem being maintained by the end caps.

6. In an insulator, a stem, including a wooden core, having a kerfed end, a sleeve enclosing the core a metal end cap threaded on the end of the sleeve, a wedge in the core kerf and compressibly held by the end cap and said cap sealing said sleeve on said core.

7. In an insulator of the class described, a stem comprising a core of relatively high tensile strength, and a plurality of dielectrically impregnated concentric tubular sleeves of fibrous material tightly assembled thereon, and means for sealing said concentric tubes over the core at the ends of the stem.

EDMUND BURKE. 

